Temporary traffic control devices such as, for example, warning and speed-limit signs are widely employed throughout the United States and elsewhere to control the movement of vehicular traffic in work-zones proximate the site of roadway or roadside construction. Because of their use in proximity to roadways, such traffic control devices are often hit by motor vehicles and so must be designed to suffer vehicular impacts without injuring any occupants of the striking motor vehicle.
Conventionally, traffic control signs comprise, as shown in FIG. 1, a stand or base including a pair of horizontally disposed legs 10 for resting on a support surface such as the ground, pavement, etc., each horizontal leg 10 further including a vertically oriented socket 11 for removably receiving therein one of a pair of upstanding supports or masts 12 to which is affixed a sign panel 13. The sign panel 13 is generally of a substantially rigid material, such as aluminum, wood, composite, etc. Sandbags S or other ballast are usually provided over top of the legs 10 to keep the traffic control sign in place in an upright orientation. The legs 10 and sockets 11 of the base, as well as the masts 12, are typically constructed of metal tubing. For the legs 10 and sockets 11, such tubing is usually of 2 inch outside dimensions; for the masts 12, the tubing is typically characterized by outside dimensions of no larger than approximately 1.75 inches. The mast 12 tubing may further include a plurality of holes 14 therein for selectively mounting the sign panel 13 in a desired position.
Generally speaking, a lower portion of the masts 12 constitutes the point of impact for a motor vehicle, and upon such impact one or both masts 12 may be sufficiently bent to become “hooked” about the striking motor vehicle's bumper. In such situations, the striking motor vehicle carries the traffic control sign forward following impact, and the forward momentum of the motor vehicle results in the accelerated rotational motion of the traffic control sign about the point of contact between the mast 12 and the motor vehicle's bumper, thereby causing the top of the mast 12, and possibly the sign panel 13, to strike the motor vehicle with considerable force.
In consequence of the foregoing, the National Cooperative Highway Research Program (“NCHRP”) has established crashworthiness standards for all work-zone traffic control devices, which standards have further been adopted by the Federal Highway Administration (“FWHA”) in respect of the National Highway System (“NHS”). These standards are embodied in NCHRP Report 350: “Recommended Procedures for the Safety Performance Evaluation of Highway Features” (National Academy Press, 1993), the disclosure of which is incorporated herein by reference in its entirety. In respect of traffic control signs in particular, the relevant evaluation standard is described in Test Designation 3-71. According to this standard, none of the constituent parts of the traffic control device must enter the motor vehicle's passenger compartment, or otherwise deform that compartment to an extent that might cause serious injury to the motor vehicle's occupant.
In light of these crashworthiness standards, the transportation-regulating bodies of some states have redefined their own standards for traffic control devices which can be deployed on the roads within their jurisdiction, including roads of the NHS, to comply with the standards set out by the NCHRP. In the State of Michigan, for instance, there has recently been developed by the Michigan Department of Transportation (“MDOT”) a new standard for portable traffic control signs which has been determined to comply with the aforementioned standards. By this new standard, the conventional traffic control sign as discussed previously in conjunction with FIG. 1 has been modified to include, inter cilia, masts of 1.75 inch outside diameter having disposed over a part of the length thereof stiffening tubing of 1.96 inch outside diameter. Unfortunately, this traffic control sign is occasioned by several drawbacks. Firstly, the sign is, by its modified construction, both heavier and more bulky, in consequence of which it is also less easily man-portable. Secondly, the thus modified traffic control sign incorporates components—namely, the masts and stiffening tubes—not found in much of the considerable existing inventory of traffic control devices owned by the many private businesses responsible for deploying traffic control devices in work-zones throughout the country. On the contrary, and as previously discussed, such existing inventory of traffic control signs are characterized by masts having outside diameters of less than 1.75 inches, and most typically on the order of approximately 1.5 inches. In view of this fact in particular, it will be necessary for the concerned private businesses to replace or significantly modify their existing inventories of traffic control signs in order to comply with the safety guidelines established by the NHWA, MDOT, and numerous other states.
In light of the above, it would be desirable to provide a means for modifying the considerable existing inventory of traffic control signs to bring the same into compliance with crashworthiness standards with the least possible expense, which means do not render the modified signs considerably less man-portable.